The end of a coking cycle is usually defined by specifying the temperature to which the center of the coke mass must be heated, typically 1800.degree. F. Since it is not practical to insert thermocouples into the coke mass in every coking cycle to directly obtain a temperature reading, indirect methods have been used in an attempt to determine the end of the coking cycle. For example, thermocouples have been placed above the coke mass and into the piping carrying the gas given off by the coal during the coking cycle.
Conventionally, the end of a coking cycle is determined by adding a predetermined time period to the time at which the thermocouples indicate a drop in the temperature. The drop in temperature indicates that hot gases no longer flow from the coke mass through the piping. If the cessation of gas flow is due to the end of devolatilization of the coal, the remainder of the coking cycle is devoted to bringing the coke mass to the required temperature. However, if the drop in temperature is due to other reasons, e.g. operating procedures which divert gas flow from one piping arrangement at one side of a coke oven to the other side, the thermocouples may indicate a drop in temperature and suggest that devolatilization of the coal mass has ended when in fact it has not ended. As a result, the coke mass would be pushed from the coke oven too soon. Upon seeing that the coke mass was pushed too soon, the coke oven operator may overcompensate by allowing an excessive coking time which reduces the production rate of coke or increasing the underfiring rate thus overheating the coke mass.
Thus there is a need for an apparatus and method to more accurately determine the true devolatilization end-point which apparatus and method are not affected by operating procedures including diverting gas flow from the coke mass.